Tuberculosis (TB), a chronic infectious disease caused by Mycobacterium tuberculosis, is primarily airborne and remains a global health problem, especially in resource-limited countries and regions. The emergence of drug resistance in M. tuberculosis has rendered the existing means ineffective in the treatment of TB. Therefore, research in new therapeutic directions has become imperative. In this review, we outline functional peptides in terms of the mechanisms of action, anti-TB attempts, advantages and disadvantages, and latest advances, aiming to analyze the research progress in anti-TB peptides. Furthermore, we investigate the potential applications of bioactive compounds found in traditional Chinese Medicine within the context of peptides.
| (1) | Amino acid composition and sequence: The properties (e.g., charge, hydrophobicity, and polarity) of different amino acids affect the structures of AMPs and their interaction with bacterial membranes.[54,55] |
| (2) | Secondary structure: The structural variants of AMPs are called secondary structures, including α-helices, β-strands with 1 or more disulfide bonds, loops, and extensions.[23] Secondary structures such as α-helices, β-folds, and loops play important roles in antimicrobial activity. α-Helices facilitate insertion into bacterial membranes, while β-folds may provide a more stable framework. The broad-spectrum resistance of AMPs is enhanced by the diversity of secondary structures. |
| (3) | Cationic structure: AMPs are usually positively charged (there is an excess of positively charged amino acids, lysine and arginine, in AMPs)[6,56] and are called cationic AMPs. These positively charged AMPs interact with negatively charged cell membranes through electrostatic interactions and undergo membrane adsorption and conformational changes.[6] The cationic structure enables antimicrobial peptides to interact with bacterial membranes, which are negatively charged, resulting in the disruption of bacterial cell walls.[57] Studies have shown that changing the cationic structure of AMPs can enhance their biological activity, thus improving the anti-microbial effect.[58-61] |
| (4) | Hydrophobicity and amphiphilicity: The hydrophobicity of AMPs has a major impact on their interaction with bacterial membranes. The hydrophobic ends of AMPs can be inserted into the bacterial plasma membrane by means of the flexibility of the linkage structure in the molecule,[40] thereby disrupting the bacterial outer membrane and leading to bacterial cell rupture, protoplasmic leakage, and death.[41] The amphiphilicity of AMPs, the ability to have both hydrophilic and hydrophobic portions, facilitates transmembrane permeation and membrane disruption.[62] The hydrophobic portion of the peptide facilitates insertion into the hydrophobic bacterial membrane, while the hydrophilic portion facilitates interaction with the membrane surface. These structural features contribute to the effective binding and disruption of bacterial membranes by AMPs. |
| (5) | Peptide modification: Chemical modifications (including methylation, phosphorylation, and glycosylation) of AMPs can alter their physicochemical properties and thus affect their antimicrobial activity.[63] In addition, factors affecting the functional activity of AMPs include length,[59] environmental conditions, and stability. |
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |